单一职责原则

src/main/java/top/fjy8018/designpattern/principle/singleresponsibility/after/CourseImpl.java

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+package top.fjy8018.designpattern.principle.singleresponsibility.after;
+
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * 课程实现类
+ * 接口实现单一职责后可以通过实现类多重实现的方式组合
+ *
+ * @author F嘉阳
+ * @date 2018-09-22 10:46
+ */
+@Slf4j
+public class CourseImpl implements CourseInfo, CourseManagement {
+    @Override
+    public String getCourseName() {
+        return "设计模式课程";
+    }
+
+    @Override
+    public byte[] getCourseVideo() {
+        return new byte[0];
+    }
+
+    @Override
+    public void paid() {
+        log.info("支付成功");
+    }
+
+    @Override
+    public void studyCourse() {
+        log.info("学习课程");
+    }
+}

src/main/java/top/fjy8018/designpattern/principle/singleresponsibility/after/CourseInfo.java

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+package top.fjy8018.designpattern.principle.singleresponsibility.after;
+
+/**
+ * 一个接口变更，只对一个实现类有影响，对其他接口无关
+ * 只承担课程信息相关职责
+ *
+ * @author F嘉阳
+ * @date 2018-09-22 10:45
+ */
+public interface CourseInfo {
+    String getCourseName();
+
+    byte[] getCourseVideo();
+}

src/main/java/top/fjy8018/designpattern/principle/singleresponsibility/after/CourseManagement.java

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+package top.fjy8018.designpattern.principle.singleresponsibility.after;
+
+/**
+ * 只承担课程管理相关职责
+ *
+ * @author F嘉阳
+ * @date 2018-09-22 10:46
+ */
+public interface CourseManagement {
+    void paid();
+
+    void studyCourse();
+}

src/main/java/top/fjy8018/designpattern/principle/singleresponsibility/after/FlyBird.java

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+package top.fjy8018.designpattern.principle.singleresponsibility.after;
+
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * 当前类只承担一个职责：飞
+ *
+ * @author F嘉阳
+ * @date 2018-09-22 10:40
+ */
+@Slf4j
+public class FlyBird {
+    public void mainMoveMode(String name) {
+        log.info("{}用翅膀飞", name);
+    }
+}

src/main/java/top/fjy8018/designpattern/principle/singleresponsibility/after/Method.java

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+package top.fjy8018.designpattern.principle.singleresponsibility.after;
+
+/**
+ * 方法单一职责
+ *
+ * @author F嘉阳
+ * @date 2018-09-22 10:57
+ */
+public class Method {
+    private String name;
+    private Integer age;
+
+    /**
+     * 此时该方法承担一个职责：更新名字
+     *
+     * @param name
+     */
+    public void updateUserName(String name) {
+        this.name = name;
+    }
+
+    /**
+     * 只更新年龄
+     *
+     * @param age
+     */
+    public void updateUserAge(Integer age) {
+        this.age = age;
+    }
+
+    /**
+     * 对于有布尔值的方法也建议拆分
+     *
+     * @param name
+     * @param bool
+     */
+    public void updateProperties(String name, boolean bool) {
+        if (bool) {
+            // TODO
+        } else {
+            // TODO
+        }
+        this.name = name;
+    }
+}

src/main/java/top/fjy8018/designpattern/principle/singleresponsibility/after/WalkBird.java

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+package top.fjy8018.designpattern.principle.singleresponsibility.after;
+
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * 当前类只承担一个职责：走
+ *
+ * @author F嘉阳
+ * @date 2018-09-22 10:40
+ */
+@Slf4j
+public class WalkBird {
+    public void mainMoveMode(String name) {
+        log.info("{}用脚走", name);
+    }
+}

src/main/java/top/fjy8018/designpattern/principle/singleresponsibility/before/Bird.java

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+package top.fjy8018.designpattern.principle.singleresponsibility.before;
+
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * 单一职责：一个类应该只有一个发生变化的原因
+ *
+ * @author F嘉阳
+ * @date 2018-09-22 10:35
+ */
+@Slf4j
+public class Bird {
+    /**
+     * 当前类有两个职责：走和飞
+     * 没有使用单一职责当业务变更必须修改代码，带来风险
+     *
+     * @param name
+     */
+    public void mainMoveMode(String name) {
+        if ("鸵鸟".equals(name)) {
+            log.info("{}用脚走", name);
+        } else {
+            log.info("{}用翅膀飞", name);
+        }
+        // 当边界值越来越多（承担更多职责）的时候变更变得更加困难
+    }
+}

src/main/java/top/fjy8018/designpattern/principle/singleresponsibility/before/Method.java

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+package top.fjy8018.designpattern.principle.singleresponsibility.before;
+
+/**
+ * 方法单一职责
+ *
+ * @author F嘉阳
+ * @date 2018-09-22 10:57
+ */
+public class Method {
+    private String name;
+    private Integer age;
+
+    /**
+     * 此时该方法承担两个职责：更新名字和年龄
+     *
+     * @param name
+     * @param age
+     */
+    public void updateUserInfo(String name, Integer age) {
+        this.name = name;
+        this.age = age;
+    }
+
+    /**
+     * 承担多个职责，同时包含可变参数，即不一定更新哪些属性
+     *
+     * @param name
+     * @param properties
+     */
+    public void updateProperties(String name, String... properties) {
+        // TODO 更新用户名和属性
+    }
+}

src/main/java/top/fjy8018/designpattern/principle/singleresponsibility/before/SCourse.java

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+package top.fjy8018.designpattern.principle.singleresponsibility.before;
+
+/**
+ * 接口单一职责
+ * 当前接口承担多个职责
+ *
+ * @author F嘉阳
+ * @date 2018-09-22 10:43
+ */
+public interface SCourse {
+    /**
+     * 课程信息相关职责
+     */
+    String getCourseName();
+
+    byte[] getCourseVideo();
+
+    /**
+     * 课程管理相关职责
+     */
+    void paid();
+
+    void studyCourse();
+}

src/test/java/top/fjy8018/designpattern/principle/singleresponsibility/before/BirdTest.java

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+package top.fjy8018.designpattern.principle.singleresponsibility.before;
+
+import org.junit.jupiter.api.Test;
+import top.fjy8018.designpattern.principle.singleresponsibility.after.FlyBird;
+import top.fjy8018.designpattern.principle.singleresponsibility.after.WalkBird;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class BirdTest {
+
+    /**
+     * 没有使用单一职责情况
+     */
+    @Test
+    void mainMoveModeBefore() {
+        Bird bird = new Bird();
+        bird.mainMoveMode("大雁");
+        // 业务变更
+        bird.mainMoveMode("鸵鸟");
+    }
+
+    /**
+     * 使用单一职责后
+     * 不同职责调用交由应用层负责
+     */
+    @Test
+    void mainMoveModeAfter() {
+        FlyBird flyBird = new FlyBird();
+        flyBird.mainMoveMode("大雁");
+        WalkBird walkBird = new WalkBird();
+        walkBird.mainMoveMode("鸵鸟");
+    }
+}